Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$246.63	9.722%	$270.6074	$270.61	$270.60	$270.60
Purchase #2	$23.59	11.872%	$26.3906	$26.39	$26.40	$26.40
Purchase #3	$113.87	12.842%	$128.4932	$128.49	$128.50	$128.50
Purchase #4	$196.40	10.347%	$216.7215	$216.72	$216.70	$216.70
Purchase #5	$55.59	7.745%	$59.8954	$59.90	$59.90	$59.90
Purchase #6	$198.34	11.526%	$221.2007	$221.20	$221.20	$221.20
Purchase #7	$85.34	7.400%	$91.6552	$91.66	$91.65	$91.70
7 purchase totals =	$919.76		$1,014.9640	$1,014.97	$1,014.95	$1,015.00